Electronic equipment during operation generates heat which must be dissipated to maintain the components and circuitry therein within predetermined design temperature limitations for proper performance. The provision of adequate cooling to electronic equipment is a recurrent design problem which has intensified with the use of integrated circuits and miniaturization of circuitry leading to greater circuit density and thus higher heat loads within smaller volumes. Cooling by forced air or even by circulation of liquid coolants often is inadequate.
The difficulties associated with adequate cooling in electronic equipment are particularly critical in the case of high speed electronic digital computers. Such computers are typically utilized in complex scientific or mathematic applications and are capable of performing millions of operations in a very short period of time. Computers of this type incorporate extensive circuitry and numerous logic and memory devices. The circuitry and components are designed and selected primarily for high speed operation, rather than low heat dissipation. Short circuit distances are an important factor in the speed attainable for operations of this magnitude. As a result, high speed electronic digital computers tend to have especially high circuit densities and thus high heat loads, and the trend is toward machines of even greater capability.
U.S. Pat. No. 4,120,021 to Cray Research, the assignee hereof, shows a cooling system for electronic assemblies in a computer. In this system a pair of circuit board assemblies are located on opposite sides of a heat conducting plate which is secured between the slotted surfaces of refrigerated cooling bars. Heat transfer is primarily by radiation and convection across the minimum air gaps between the circuit board assemblies and the cooling plate, and to some small extent also by incidental conduction through the mechanical connectors. This system functions well and provides good cooling capacity sufficient for many computers, but it does not have adequate capacity to meet the cooling needs of the latest computers and it does not satisfactorily address the problem of heat distribution. Some devices on a circuit board dissipate more heat than others such that proper cooling requires sufficient heat transfer as well as distribution.
A need has thus arisen for an improved circuit module of better heat transfer and distribution capability.